Wear resistant deposited steel

ABSTRACT

Hard and wear resistant deposited steel including martensite base and vanadium-carbide dispersed therein with the amount of vanadium of 32 to 40 percent in weight. A method for producing the hard and wear resistant steel, said method comprising steps of compression forming powder materials into a welding rod, melting the rod in a non-oxidizing atmosphere by means of a heat produced by an electric arc discharge, and heat treating the solidified substance thus obtained. The invention further provides a novel use of the steel thus produced.

limited States Patent [191 lshihara et a1.

[ 1 Mar. 4, 1975 WEAR RESISTANT DEPOSITED STEEL Inventors:

Assignee:

Filed:

Appl. No.

J00 lshihara; l-liromi Kagohara; Masaichi Nagai, all of Hitachi; YasushiOhuchi, Katsuta, all of Japan Hitachi, Ltd., Tokyo, Japan Jan. 18, 1973Foreign Application Priority Data Jan. 19, 1972 US. Cl 148/315, 29/196,29/196.1, 29/198, 75/123 J, 75/128 D, 148/34, 29/191.4, 219/145 Int.Cl... C22c 39/50, B32b 15/04, B32b 15/18 Field of Search 29/196, 196.1,198, 191.4, 29/191.2, 196.2, 196.3, 196.4, 196.5, 196.6;219/145,146,147;l48/31.5,34, 127,143, 142; 75/122, 134 V, 126 E, 128 V,123 J,

References Cited UNITED STATES PATENTS Japan 47-6970 Siever 219/1461,942,364 1/1934 Rood 219/146 2,016,585 10/1935 Busore et a1. 219/1462,219,462 10/1940 Wissler 219/145 3,514,272 5/1970 Cook 29/196 X FOREIGNPATENTS OR APPLlCATlONS 529,190 8/1956 Canada 75/134 V PrimaryE.\-aminerCharles N. Lovell Attorney, Agent, or Firnz-Craig & Antonelli[57] ABSTRACT 6 Claims, 6 Drawing Figures PATENIEDHAR 4|s75 SHEET 1 OF 5FIG. lb

PATENTEU 4|975 3,869.319

sum 3 o 5 HARMESS F/G. 4 Na 8 TEMPERATURE OF OUENCH/NG (6) The presentinvention relates to a novel steel composition which has-an excellentwear resistant property and which can be easily formed into a desiredshape. The present invention also relates to a method for producing sucha novel steel.

Hithertofore, a wear resistant high speed tool steel including 1.2weight percent of vanadium, 19 weight percent of tungsten and 5.5 weightpercent of cobalt has been known as SKH3 steel in Japanese IndustrialStandard (.IIS) which corresponds to T4 in AISI standard. However, sincethis steel includes an increased amount of tungsten and cobalt, it isnot so cheap. Further, the steel is insufficient in wear resistantproperty.

In order to provide an improved wear resistant property, there has beenproposed to provide a steel including 12 weight percent of vanadium, 1weight percent of chromium, 1 weight percentof molybdenum and 3.25weight percent of carbon. However, this steel includes an increasedamount of vanadium-carbide produced therein, so that it has inferiormelting, casting and forging properties. Thus, the steel of this typehas not been widely used in industry.

From the view point of wear resistant property, the most superior knownmaterial is an alloy produced through a sintering technique from powderof tungstencarbide. However, since this alloy is a sintered material, itcannot be formed into a complicated shape. Further, it is difficult toprovide a uniform particle size of tungsten-carbide particles and thesurfaces of the particles are undesirably subjected to oxydization.Moreover, tungsten is very expensive. Thus, the sintered alloy of thistype has only a limited use.

Therefore, the inventors performed efforts to develope a material whichis comparable in the wear resistant property to said sintered hard alloyand which is easy to form but less expensive to manufacture. Theinventors paid their attention to the fact that vanadium carbide(hereinafter designated at VC) has a hardness of Viskerse 2,800 which iscomparable to the hardness of tungsten-carbide which is Viskerse 2,700to 2,800, while the cost per unit weight of VC is about one-fifth ofthat of tungsten-carbide, and that VC is about onethird in specificweight as compared with tungsten carbide so that the use of VC is veryeconomical when it is used with the same amount as tungsten carbide isused.

Therefore, the inventors investigated various types of steels includingVC and found that, as the amount of VC dispersed in ferrite baseincreases, the size of educed VC increases and there is produced a welldeveloped dendrite structure having an elongated stem and a plurality ofbranches with 20 to 30 weight percent of VC content. Such a dendritestructure often causes a stress concentration and breakage propagatestherefrom. With the VC content exceeding 30 percent, adjacent VCcomponents interfers with each other pre venting the formation of anelongated dendrite structure, and VC appears in a particulated phasedispersed in the base. Such a steel including an increased amount of VChas an increased hardness and an excellent wear resistant property, andcan be produced with a lower cost. Therefore, the steel of this typewill provide a practical advantage if it can be industrially produced.The present invention provides a novel steel composition having anincreased amount of VC, and a method for producing such a steel.

SUMMARY OF THE INVENTION The present invention has an object to providea novel metal composition having an excellent wear resistant propertywhich is comparable to that of sintered tungsten-carbide alloy steel.

Another object of the present invention is to provide a method forproducing a highly wear resistant iron based metal including 32 to 40weight percent of vanadium and 6.7 to 8.6 weight percent of carbon.

A further object of the present invention is to provide a tool and aslidable part which has a less expensively formed wear resistantdeposit-welded portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la and b are microscopicphotographs for showing the effect of vanadium-carbide in metalstructure, in which FIG. 1a shows a structure having less educedvanadium-carbide and FIG. lb shows a structure having an increasedamount of vanadiumcarbide;

FIG. 2 is a diagram showing the relationship between quenchingtemperature and hardness with various nickel contents;

FIG. 3 is a diagram showing the relationship between quenchingtemperature and hardness with various manganese contents;

FIG. 4 is a diagram showing the relationship between quenchingtemperature and hardness with various carbon contents; and,

FIG. 5 is a diagram showing the relationship between quenchingtemperature and hardness with various chromium contents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relatesto a steel composition having a superior wear resistant property, andprovides a deposited steel and a method for manufacturing the same bymelting and thereafter solidifying the materials which is then heattreated to form vanadium carbide phase uniformly educed in themartensite matrix.

According to the present invention, there is provided a deposited steelcomposition including 32 to 40 percent of vanadium, 2 to 4 percent ofnickel, and 0.5 to 3 percent of manganese, the balance being steel andimpurities with carbon content 0.3 to 0.6 percent higher than one-fifthof the weight of vanadium, said steel being characterized by having analloy structure including vanadium-carbide educed in a matrix mainlycomprising martensite. In accordance with the present invention, thecomposition of the steel is so adjusted that it can well be heat treatedeven if the formation of vanadium-carbide is increased, so as to providea structure having a superior wear resistant property.

Throughout the specification, the term *deposited steel or metalcomposition is used to mean a material deposited on a substrate in sucha manner that it does not receive any adverse effect such as dillutionfrom the substrate.

According to the present invention, the amount of vanadium content is 32to 40 weight percent. With vanadium exceeding 40 weight percent,satisfactory heat treatment cannot be performed even if the amounts ofother components are sufficiently adjusted, so that the steel cannotattain sufficient hardness. Further, when vanadium contents exceeds 40weight percent, a uniform deposited metal structure cannot be obtainedeven if TIG welding is employed by using a nonexpendible tungstenelectrode. With vanadium content less than 32 weight percent, the educedvanadiumcarbide is developed into an extended dendrite structure. Inthis area, stress concentration is produced and cracks are developedtherefrom.

FIG. la shows in a microscopic photograph a deposited metal including27.5 percent of vanadium, 50 percent of chromium, 0.5 percent ofmanganese, 0.7 percent of silicon, 6.2 percent of carbon and the balanceiron. From FIG. '10, it will be notedthat the metalstructure has a welldeveloped dendrite structure including an elongated stem portion andbranches extending perpendicularly therefrom. FIG. lb shows in amicroscopic photograph an example of the deposited metal in accordancewith the present invention, which includes 37.2 percent of vanadium, 2.8percent of chromium, 0.5 percent of manganese, 0.6 percent of nickel and7.84 percent of carbon. As noted in FIG. lb, the educed vanadium-carbideis relatively round and uniformly dispersed. It should be noted that,with vanadium content of 32 to 40 weight percent, a stable and uniformwear resistant property is provided in the metal and thus it is possibleto provide a satisfactory deposited metal.

Carbon is combined with vanadium to form vanadium-carbide so as toprovide a superior wear resistant property to the steel. The vanadiumcarbide is formed by approximately weight parts of vanadium andapproximately 1 weight part of carbon. In order to obtain a martensitestructure, it is required that 0.3 to 0.6

weight percent of carbon is included in the structure in the form of asolid solution. If the carbon content is less than the value referred toabove, a ferrite structure is produced during quenching. On the otherhand, an austenite structure is produced when the carbon content isgreater than the value. Therefore, in the metal structure of the presentinvention, the carbon content must be 0.3 to 0.6 weight percent higherthan one-fifth of the weight of vanadium content.

Nickel is required to provide a quenchable characteristics to the metal.A satisfactory quenchable property can be provided by 2 to 4 weightpercent of nickel. With nickel content less than the value, the hardnessof the metal is widely varied in response to the change in quenchingrate. With nickel content exceeding 4 weight percent the amount ofaustenite structure is correspondingly increased resulting in a reducedhardness.

Manganese is required in order to prevent any blow hole or otherstructural defect in the deposited steel and improve quenching property.With manganese content lower than 0.5 weight percent, it cannot providea sufficient de-oxydization power. With manganese content exceeding 3weight percent, the amount of austenite structure increases resulting inreduction in wear resistant property.

The deposited steel in accordance with the present invention isconstituted by the aforementioned components but it may advantageouslyinclude chromium to improve the wear resistant property of the steel aswell as quenching property of the matrix. However, the amount ofchromium which contributes to the quench ing property is limitedbecause, with chromium content exceeding 3 weight percent, it isimpossible to obtain a perfect martensite structure but there isproduced a ferrite structure in the matrix resulting in a remarkablereduction in the quenching property.

Phosphor, sulphur and silicon existing in the deposited steelcomposition must be as small as possible. Further, aluminum and calciummust also be as small as possible because they have adverse effects onthe weldability of the steel. The maximum allowable content of aluminumand calcium is 0.1 weight percent for each element.

The wear resistant steel in accordance with the present inventionincludes an increased amount of vanadium-carbide having a melting pointof 2,8 10C, so that 'it'cannot be molten by a conventional means such asa high frequency melting technique. Further, it cannot be formed bysintering as in the case of tungsten-carbide because it is verydifficult to reduce the surface of VC. In view of these facts, theinventors accomplished a method in which particulated materials areinstantaneously molten by subjecting them to an electric arc dischargein a non-oxydizing atmosphere to provide a steel of a desiredcomposition.

According to the method in accordance with the present invention,particulated materials uniformly mixed in such amounts that can providea composition referred to above are compression formed with an additionof binder or filled in an iron pipe to form a welding rod. When aphenollic resin is used as the binder, the carbon content in thematerials must previously be reduced because the carbon content in theresin is dissolved by the welding heat and allowed to enter the moltenmetal when the rod is molten as explained below. It has been found that,when a deposited metal is formed from a welding rod including 3 percentof phenol resin as binder, 40 to percent of carbon in the resin isretained in the metal. It should of course be noted that the rate ofcarbon retained in the metal depends on the welding condition as well asthe ratio among other elements, so that it is necessary to performexperiments to find out the rate of carbon retained in the metal.

When powder materials are put into a metal pipe, the composition of thepipe must be taken into account in determining the mixing ratio of thepowder materials because the components in the metal pipe are retainedin the deposited metal. If the wall of the metal pipe is too thick, thecomponents of the pipe may not, when molten, be completely mixed withthe molten materials which have previously put into the pipe in powderform. producing a deposited metal of a non-uniform structure. Therefore,it is required that the wall thickness of the pipe must be less than 0.3mm.

The density of the welding rod made by the powder materials must be ashigh as possible. With a lower density, the powder materials may besplashed or fallen away during welding operation. Further, the amount ofalloy structure in the deposited metal may be reduced producing abrittle vanadium-carbide in the form of an eutectic mixture. Thus, thepowder filling rate of the welding rod must exceed 60 percent.

In order to produce a deposited metal from the welding rod including asubstantial amount of VC. it is necessary to employ a welding process inwhich energy of higher density is available. Further, it is necessary toavoid to hold the materials under a high temperature for an extendedperiod in order to prevent the dendrite structure from being developed.Since the vanadium is highly affinitive to oxygen, it is also desirableto perform the process in a non-oxydizing atmosphere. For example, TIGwelding which is performed under an inactive atmosphere using anon-expendible tungsten electrode is particularly suitable for thepresent invention. The inactive gas atmosphere may not be used when aflux such as sodium carbonate, calcium fluoride or liquid glass iscoated on the outer surface of the metal pipe or mixed in the powdermaterials forming the welding rod.

There is no particular limitation on the nature of the substrate onwhich the molten metal is deposited from the welding rod. In fact, mostof iron based material can be used as the substrate of the depositedmetal in accordance with the present invention.

The metal prepared in accordance with the present invention has beendeposited on a substrate made of a mild steel and the deposited metal iscut and ground to provide a section which is to be tested by an electronprobe micro analyzer. Although there may be slight differences inaccordance with the change in the welding condition, it has been foundthat, in the region from the boundary between the deposited metal andthe substrate to a position in the deposited metal 0.5 to 1.0 mm apartfrom the boundary, there is a dillution effect of the substrate, but anyeffect of the substrate is eliminated in the area apart from theboundary by 1.5 mm or more and a satisfactory structure of the depositedmetal is obtained.

In order to increase the hardness of the deposited metal, it may besubjected to a heat treatment as required. The hardness may depend onthe metal components and the heat treatment temperature, but it ispreferable in the steel composition of the present invention to performthe heat treatment under 950C to 1,100C.

The deposited metal in accordance with the present invention may bemachined by an arc discharge or electrolytic machining process and. whena precise machining is required, it may be machined by using a diamondtool.

The steel in accordance with the present invention has an excellenthardness and wear resistant property and can readily be adapted toprovide a desired shape by means of depositing. Further, it has a strongadherence to the substrate and is less expensive to manufacture.Therefore, it can be applied to anywhere in which a conventionalsintered tungsten-carbide is used. For example, the steel in accordancewith the present invention may be used in tools, heavily loaded bearingsand cam mechanisms, control rod driving means for a nuclear reactor, andblade tips for a bull-dozer.

It is also possible to deposit the steel prepared in accordance with thepresent invention on a tough core steel to form a coating of a uniformthickness. This method may be convenient to provide rolls which may beused in a compound roll arrangement in a rolling mill. Such a big rollcannot be provided by a sintered tungsten-carbide because it lackstoughness and is expensive. Even if it is possible to provide a hollowcylindrical sintered body, it cannot be combined with a roll core with asufficient strength to provide a compound roll.

The present invention will now be described with reference to specificexamples.

EXAMPLE 1 A pipe having an inner diameter of 3 mm was prepared from amild steel plate of 0.2 mm thick. Ironvanadium alloy, graphite,manganese, silicon and chromium, each in the form ofa powder finer than50 mesh, had been mixed with an appropriate proportion and drawn througha die into a rod having an outer diameter of 2.5 mm to form a weldingrod of powder filling rate of 85 percent. The welding rod was then usedto perform an argon-arc welding with an electric current level of 140 A.The molten metal was deposited on a substrate made of a steel materialJIS-SKDI (AlSI-D3) to form a layer of 10 mm thick. The composition ofthe deposited steel is shown in Table 1. The samples 1 through 3 havebeen prepared in order to know the effect of nickel content on thequenching property of the deposited steel. The samples 4 and 5 have beenprepared to know the effect of manganese content, the samples 6 to 9 toknow the effect of the carbon content, and the samples 9 to 11 to knowthe effect of chromium.

Table 1 Composition of Deposited Steel (weight 71) FIG. 2 shows therelationship between the heat treat ment temperature and the hardness,the results being obtained from the samples 1 through 3. It was foundthat the samples 1 and 2 had higher hardness as compared with the sample3 and did not show any remarkable change in properties in accordancewith the change in tempering temperature. The sample 3 is inferior inhardness to the samples 1 and 2 and, moreover,

showed a remarkable decrease in hardness in response to the increase intempering temperature. This is considered as being caused by anincreased austenite in the matrix due to the increase in nickel content.Further, the relationship between the quenching rate and hardness hasbeen investigated with respect to the samples 1 and 2, and found thatthere is no remarkable change in the sample 2 which includes more nickelbut the hardness of the sample 1 remarkably decreases with the quenchingrate lower than l,000C/min.

FIG. 3 shows the effect of tempering temperature on the hardness of thedeposited steel as measured in the samples 4 and 5. As seen in thedrawing, as the manganese content increases, the amount of austenitestructure in the matrix increases resulting in a decrease in hardness.

FIG. 4 shows the change in hardness in response to the change intempering temperature as measured in the samples 6 through 9. Thesamples having higher carbon contents show greater hardness with thesame tempering temperature. The reason why the sample 6 is inferior inhardness to the other samples is that in this sample the carbon contentexisting in the form of solid solution is so small that the ferritestructure still exists. It should be noted that each of the samples 7through 9 which has carbon content of 0.3 to 0.6 weight percent higherthan one-fifth of vanadium content has a greater hardness. 1

FIG. 5 shows the change in hardness in response to tempering temperatureas measured in the samples 9 through 1 l. The chromium content generallyimproves heat treating and quenching property. However, in the alloysteel composition of the present invention, the effective amount ofchromium is relatively limited. According to the inventors experiments,it has been found that the chromium content up to 3 weight percent doesnot decrease the hardness, however, the sample 11 having 5 weightpercent of chromium is found to have a lower hardness.

EXAMPLE 2 EXAMPLE 3 A welding rod including 7.95 weight percent ofcarbon, 37.8 weight percent of vanadium, 3.0 weight percent of nickel,1.0 weight percent of manganese, 0.8 weight percent of silicon and thebalance iron was prepared from the same metal powders by the sameprocess as in the Example 1. The welding rod was then molten by anargon-arc welding process in the argon gas atmosphere and the moltenmetal was deposited on a rotor core punching die substrate. The currentlevel was 140 to 150 A and the thickness of the deposited layer was mm.Then the deposited metal was heated to 1,000C in a cylindrical furnacefilled by argon gas For the purpose-of comparison, a rotor core punchingdie was prepared from a dies steel JlS-SKDl (AlSl- D3) and used to puncha silicon steel plate of 0.5 mm thick. It has been found that the burrheight was 0.10 mm after 70,000 times of punching operations and the diewas already worn beyond the allowable limit.

When a punching die made of a sintered tungstencarbide was used, theburr height was 0.02 mm after 70,000 times and even after 500,000 timesof punching operations.

Thus, it has been found that the steel in accordance with the presentinvention is comparable to the sintered tungsten-carbide.

EXAMPLE 4 Ferro-vanadium, ferro-silicon, ferro-manganese,ferro-molybdenum, ferro-chromium, graphite, and powdered iron areprepared in the form of powder finer than 100 mesh and thoroughly mixedwith the existence of phenol resin. The powder materials are then formedinto a plate of 2 mm thick under a pressure of 6 ton/cm and thereaftercured by heating the plate in an electric furnace of 180C for 5 minutes.The cured plate is then closely fitted to a substrate of a mild steeland molten and deposited on the substrate by applying an electricdischarge are in an argon atmosphere. The deposited metal layer was 5.5mm thick. The deposited metal was then annealed at a temperature of 800Cfor 5 hours and cooled in furnace, thereafter it was quenched at 1,000Cand tempered at 200C. The deposited metal layer is then machined bymeans of an electrolytic machining and a diamond tool to form a metallayer which is 5.0 mm thick and has a surface area of 254 mm Thechemical components and the hardness of the deposited metal are shown inTable 2. The sample 12 is an alloy steel having vanadium-carbide contentless than that of the steel in accordance with the present invention.The samples 13 and 14 are made in accordance with the present invention.

for a certain period and thereafter taken out of the furnace to bequenched in water. The hardness of the deposited steel was H 1,100. Thedeposited steel was then annealed to a hardness of H, 980 and machinedby means of an electric discharge machining and grinding operation toform a punching die.

The punching die thus formed was used to punch a silicon steel plate of0.5 mm thick. The amount of wear of a punching die as well as those ofother dies are usually represented by the height of a burr which-appearsin the punched section of a workpiece and the die is usually consideredas being unusable when the height of the burr exceeds 0.05 mm. Theheight of the burr in the silicon steel punched by the aforementionedpunching die was 0.01 mm even after 70,000 times of punching operations.Further, it has been found that the burr height did not show anyremarkable increase even after 500,000 times of punching operations.

Thedeposited steel having the surface area of 254 mm is pushed under auniform load of 800 gr onto an abrasive surface which is rotating at aspeed of 720 r.p.m. and the amount of wear was measured after an hoursoperation. For the purpose of comparison, J IS- SKDl (AlSI-D3), SKH3(AlSl-T4) and a sintered tungsten-carbide were tested under the samecondition to measure the amount of wear.

The amount of wear of the samples 13 and 14 was two times as much asthat of the tungsten-carbide but about one-fifth of that of the sample12. Further, the amount of wear of the samples 13 and 14 was less thanone-twentieth of that of SKDI or SKH3. Thus, the alloy steel of thepresent invention can be satisfactorily used in the place of thetungsten-carbide.

Although the invention has thus been shown and described with referenceto specific examples, it should be noted that the invention is in no waylimited to the details of the described examples and the scope of theinvention is limited only by the appended claims.

We claim:

1. Wear resistant structure comprising a metal substrate and a layer ofsteel deposited thereon, said steel consisting essentially of, in weightpercent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel, and 0.5to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher thanone-fifth of the vanadium content, and the rities accompanyingtherewith, said steel having vanadium-carbide structure educed in amatrix mainly comprising martensite.

3. Wear resistant structure in accordance with claim 1, in which saidimpurities include aluminum and calcium, each being less than 0.1 weightpercent.

4. Wear resistant structure in accordance with claim 2, in which saidimpurities include aluminium and calcium, each being less than 0.1weight percent.

5. Wear resistant structure comprising a metal sub strate and a steellayer deposited thereon with a thickness more than 1.5 mm, saiddeposited steel layer having a portion free from the effect of saidsubstrate, said portion consisting essentially of, in weight percent, 32to 40 percent of vanadium, 2 to 4 percent of'nickel, 0.5 to 3 percent ofmanganese, carbon of 0.3 to 0.6 percent higher than one-fifth of thevanadium content, chromium less than 3 percent, and the balance iron andimpurities accompanying therewith, said portion further havingvanadium-carbide structure educed in a matrix mainly comprisingmartensite, said substrate having a tenacity higher than that of thedeposited steel.

6. A welding rod for producing a wear resistant deposited steelconsisting essentially of, in weight percent, 32 to 40 percent ofvanadium, 2 to 4 percent of nickel, 0.5 to 3 percent of manganese,carbon of 0.3 to 0.6 percent higher than one-fifth of the vanadiumc0ntent, and the balance iron and impurities accompanying therewith,said welding rod comprising an iron based metal pipe having a wallthickness less than 0.3 mm, said vanadium, nickel, manganese, carbon andiron being filled in powder form in said pipe with a filling rate atleast percent.

1. WEAR RESISTANT STRUCTURE COMPRISING A METAL SUBSTRATE AND A LAYER OFSTEEL DEPOSITED THEREON, SAID SHEET CONSISTING ESSENTIALLY OF, IN WEIGHTPERCENT, 32 TO 40 PERCENT OF VANADIUM, 2 TO 4 PERCENT OF NICKEL, AND 0.5TO 3 PERCENT OF MANGANESE, CARBON OF 0.3 TO 0.6 PERCENT HIGHER THANONE-FIFTH OF THE VANADIUM CONTENT, AND THE BALANCE BEING IRON ANDIMPURITIES ACCOMPANYING THEREWITH, SAID STEEL HAVING VANADIUM-CARBIDESTRUCTURE EDUCED IN A MATRIX MAINLY COMPRISING MARTENSITE.
 2. Wearresistant structure comprising a metal substrate and a layer of steeldeposited thereon, said steel including, in weight percent, 32 to 40percent of vanadium, 2 to 4 percent of nickel, and 0.5 to 3 percent ofmanganese, carbon of 0.3 to 0.6 percent higher than one-fifth of thevanadium content, and chromium less than 0.3 percent, and the balancebeing iron and impurities accompanying therewith, said steel havingvanadium-carbide structure educed in a matrix mainly comprisingmartensite.
 3. Wear resistant structure in accordance with claim 1, inwhich said impurities include aluminum and calcium, each being less than0.1 weight percent.
 4. Wear resistant structure in accordance with claim2, in which said impurities include aluminium and calcium, each beingless than 0.1 weight percent.
 5. Wear resistant structure comprising ametal substrate and a steel layer deposited thereon with a thicknessmore than 1.5 mm, said deposited steel layer having a portion free fromthe effect of said substrate, said portion consisting essentially of, inweight percent, 32 to 40 percent of vanadium, 2 to 4 percent of nickel,0.5 to 3 percent of manganese, carbon of 0.3 to 0.6 percent higher thanone-fifth of the vanadium content, chromium less than 3 percent, and thebalance iron and impurities accompanying therewith, said portion furtherhaving vanadium-carbide structure educed in a matrix mainly comprisingmartensite, said substrate having a tenacity higher than that of thedeposited steel.
 6. A welding rod for producing a wear resistantdeposited steel consisting essentially of, in weight percent, 32 to 40percent of vanadium, 2 to 4 percent of nickel, 0.5 to 3 percent ofmanganese, carbon of 0.3 to 0.6 percent higher than one-fifth of thevanadium content, and the balance iron and impurities accompanyingtherewith, said welding rod comprising an iron based metal pipe having awall thickness less than 0.3 mm, said vanadium, nickel, manganese,carbon and iron being filled in powder form in said pipe with a fillingrate at least 60 percent.